Holism is a term introduced by Smuts, in contrast to individualism and wholism. In the context of evolution it emphasises co-evolution between parts and wholes, with neither being dominant. The best explanation I have found is:

“Back in the days of those Ancient Greeks, Aristotle (384-322BCE) gave us:

The whole is greater than the sum of its parts; (the composition law)The part is more than a fraction of the whole. (the decomposition law)

Smuts also develops LLoyd Morgan’s concept of emergence, For example, the evolutionary ‘fitness function’ may emerge from a co-adaptation rather than be fixed.

The book covers evolution from physics to personality. Smuts intended a sequel covering, for example, social and political evolution, but was distracted by the second world war, for example.

Smuts noted that according to the popular view of evolution, one would expect organisms to become more and more adapted to their environmental niches, whereas they were more ‘adapted to adapt’, particularly mankind. There seemed to be inheritance of variability in offspring as whole as the more familiar inheritance of manifest characteristics, which suggested more sudden changes in the environment than had been assumed. This led Smuts to support research into the Wegner hypothesis (concerning continental drift) and the geographic origins of life-forms.